NOx SENSING CHARACTERISTICS OF MIXED-POTENTIAL-TYPE ZIRCONIA SENSOR USING NiO SENSING ELECTRODE AT HIGH TEMPERATURES

A stabilised-zirconia-based NOx sensor attached to an oxide sensing-electrode (SE) was tested for the detection of NOx at temperatures higher than 800 C for car-emission control applications. Among various oxide SEs tested, NiO was found to give the highest sensitivity to NO2 even at high temperatures. It was found that the sensor using NiO-SE showed quicker recovery in the presence of water vapour, compared with that in the dry sample gas. Electromotive force values of 57 and 75 mV were observed, respectively, under dry and wet (5 vol% water vapour) conditions with 400 ppm NO2 at 850 C. 22 refs.